JAXP使用Stax API时格式化输出XML 2

之前实现的一个版本：http://www.cnblogs.com/lyhtbc/p/jaxp-pretty-format-validate-validation-stax-stax2.html

这个版本中存一个问题：如果某一个节点的值是空的话，会换行输出结束标签，如：

<a>

</a>

某些场景下会要求节点内必须要有值，否则就应该输出为 <a/>（例如XBRL instance的schemaLink节点）。

新代码如下：

XMLPrettyFormatter:

 import javax.xml.stream.XMLStreamException;

 /**
  * XML pretty formatter.
  */
 public interface XMLPrettyFormatter {

     enum NodeType {
         ELEMENT, VALUE, NULL
     }

     String DEFAULT_INDENTION = "\t";

     void writeStartElementIndention() throws XMLStreamException;

     /**
      * @param blankValue
      *            True if the value is null of blank character.
      */
     void writeValueIndention(boolean blankValue) throws XMLStreamException;

     void writeEndElementIndention() throws XMLStreamException;

 }

DefaultPrettyFormatter:

 import java.util.LinkedList;

 import javax.xml.stream.XMLStreamException;

 import org.codehaus.stax2.XMLStreamWriter2;

 /**
  * Default XML pretty formatter.
  * <ol>
  * <li>Default intention is tab character "\t".</li>
  * <li>The value display in the same line with which element it belongs to.</li>
  * <li>If value is blank, don't use separate end tag.</li>
  * </ol>
  */
 public class DefaultPrettyFormatter implements XMLPrettyFormatter {

     private String indent = DEFAULT_INDENTION;

     private LinkedList<NodeType> stack = new LinkedList<XMLPrettyFormatter.NodeType>();

     private XMLStreamWriter2 writer;

     public DefaultPrettyFormatter(XMLStreamWriter2 writer) {
         this.writer = writer;
     }

     public DefaultPrettyFormatter(XMLStreamWriter2 writer, String indent) {
         this.writer = writer;
         this.indent = indent;
     }

     @Override
     public void writeStartElementIndention() throws XMLStreamException {
         NodeType lastNode = stack.peek();
         if (lastNode != null && lastNode == NodeType.NULL) {
             stack.pop();
         }

         writeLineBreaker();
         for (int i = 0; i < stack.size(); ++i) {
             writeIndention();
         }

         stack.push(NodeType.ELEMENT);

         // default value node
         stack.push(NodeType.NULL);
     }

     @Override
     public void writeValueIndention(boolean blankValue) throws XMLStreamException {
         if (!blankValue) {
             // if value is not blank, pop default blank node first.
             stack.pop();
             stack.push(NodeType.VALUE);
         }
     }

     @Override
     public void writeEndElementIndention() throws XMLStreamException {
         NodeType lastNode = stack.pop();
         if (lastNode == NodeType.ELEMENT) {
             writeLineBreaker();
             for (int i = 0; i < stack.size(); ++i) {
                 writeIndention();
             }
         } else {
             // pop start element
             stack.pop();
         }
     }

     private void writeLineBreaker() throws XMLStreamException {
         writer.writeCharacters("\n");
     }

     private void writeIndention() throws XMLStreamException {
         writer.writeCharacters(indent.toCharArray(), 0, indent.length());
     }

 }